i have been testing out Blender and Jahshaka lately. Heres a mattepainter's review...(i'll add more later when I can).

Blender:

- Fast modeler that requires some getting used too. Should not be considered a replacement to another package but rather a tool at the beginning of the pipeline.
- Sculpting is great and actually works better than another $300 pakage.
- compositing for materials works well, compositing images mode is awesome for keying but can't do a 2.5d camera comp because of jitter problems.
-Other compositing software could learn something from the node interface. Blenders node knots are awesome. node groups are very cool.
- it took 2 hors to do something in the blender compositor that takes 6 minutes in Shake.
- uses camera sticky instead of mapping and makes 2.5d shots hard but can produce great results.

Jahshaka:
only good for conceptualizing because of its lack of resolution independance and compressed image output.
Even on a dual core g5 some things always crash and never work.
- i did a camera move and the result was only ok.